correct.jsx

import React, { useRef, useEffect } from 'react';

const ExternalScript = ({ src }) => {
  const ref = useRef();

  useEffect(() => {
    const scriptEl = document.createElement("script");
    scriptEl.src = src;
    ref.current.append(scriptEl);
  }, [src]);

  return <div ref={ref} />;
};

const Hello = () => {
  return (
    <div>
      <h1>Hello, Medium</h1>
      {/* This does work */}
      <ExternalScript src="//google.com/somescript.js" />
    </div>
  );
};